Piperazine derivatives and processes for preparation thereof

ABSTRACT

This invention provides compounds of the following formula   WHEREIN R1 is a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a hydroxyalkyl group having 2 to 4 carbon atoms, a benzyl group, a benzyl group substituted by methoxy, a phenyl group, a propargyl group or an acyl group; R2 is a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkyl group having 2 to 4 carbon atoms substituted by hydroxy or halogen, a vinyl group, an allyl group, or a benzyl group R3 is a hydrogen atom or an alkyl group having 1 to 6 carbon atoms; AND SALTS THEREOF, AND PROCESSES FOR PREPARING THEM. Some of the compounds have antibacterial activities.

Unite States atet [1 1 Minami et al.

[ June 3,1975

[73] Assignee: Dainippon Pharmaceutical Co. Ltd.,

Osaka, Japan [22] Filed: Aug. 8, 1973 [21] Appl. No.: 386,626

[30] Foreign Application Priority Data Aug. 14, 1972 Japan 47-81288 [52] US. Cl ..260/256.4 F; 260/256.4 N;

260/268 C; 260/268 PH; 260/268 H;

[51] Int. Cl C07d 51/42 [58] Field of Search 260/256.4 F

[56] References Cited UNITED STATES PATENTS 3,320,257 5/1967 Lesher 260/256.4 F

3,725,405 4/1973 Santilli et al. 260/256.4 F

3,753,993 8/1973 Lesher et a1. 260/287 3,770,742 11/1973 Matsumoto et a1. 260/256.4 F

Primary Examiner-Donald G. Daus Assistant Examiner-James H. Turnipseed Attorney, Agent, or F irm-Sherman & Shalloway [5 7 ABSTRACT This invention provides compounds of the following formula 0 gm g rcooa R-"l 4 3 i l \e 7/ N/\1}l wherein R is a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a hydroxyalkyl group having 2 to 4 carbon atoms, a benzyl group, a benzyl group substituted by methoxy, a phenyl group, a propargyl group or an acyl group; R is a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkyl group having 2 to 4 carbon atoms substituted by hydroxy or halogen, a vinyl group, an allyl group, or a benzyl group R is a hydrogen atom or an alkyl group having 1 to 6 carbon atoms;

and salts thereof, and processes for preparing them. Some of the compounds have antibacterial activities.

12 Claims, No Drawings PIPERAZINE DERIVATIVES AND PROCESSES FOR PREPARATION THEREOF This invention relates to new and useful piperazine derivatives having antibacterial activities, intermediates thereof, processes for preparing them, and also to their use.

This invention provides compounds of the following formula wherein R is a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a hydroxyalkyl group having 2 to 4 carbon atoms, a benzyl group, a benzyl group substituted by methoxy, a phenyl group, a propargyl group or an acyl group; R is a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkyl group having 2 to 4 carbon atoms substituted by hydroxy or halogen, a vinyl group, an allyl group, or a benzyl group R is a hydrogen atom or an alkyl group having 1 to 6 carbon atoms;

and salts thereof.

The term acyl group, as used in the present specification and appended claims, denotes a carbonic or carboxylic acid residue such as a lower alkanoyl group such as formyl, acetyl, trifluoroacetyl, or propionyl, a lower alkoxycarbonyl group such as methoxycarbonyl or ethoxycarbonyl, and a phenyl-substituted lower alkoxycarbonyl group, e.g. benzyloxycarbonyl.

In the present specification and appended claims, the term lower alkyl group either in itself or as part of other groups denotes an alkyl group containing 1 to 4 carbon atoms.

Of the compounds of formula [I] the following compounds and salts thereof are suitable as antibacterial agents.

In this formula R is a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a hydroxyalkyl group having 2 to 4 carbon atoms, a phenyl group or a propargyl group; and R is an alkyl group having 1 to 4 carbon atoms, an alkyl group having 2 to 4 carbon atoms substituted by hydroxy or halogen, a vinyl group, an ally] group, or a benzyl group.

Especially suitable compounds of this invention as antibacterial agents are shown below.

5,8-Dihydro-8-ethyl-2-( l-piperazinyl)-5-oxopyrido [2,3-]pyrimidine-6-carboxylic acid,

5 ,8-dihydro-8-ethyl-2-( 4-ethyll -piperazinyl )-5- oxopyridol2,3-d]pyrimidine-6-carboxylic acid,

8-benzyl-5,8-dihydro-2-( l-piperazinyl)-5- oxopyrido[2,3-d]pyrimidine-6-carboxylic acid,

5,8-dihydro-2-( l-piperazinyl)-8-vinyl-5-oxopyrido [2,3-d]pyrimidine-6-carboxylic acid,

8-(2-chloroethyl)-5,8-dihydro-2-( l-piperazinyl)-5- oxopyrido[2,3-d]pyrimidine-6-carboxylic acid, and

pharmaceutically acceptable acid addition salts or alkali metal salts of these compounds.

The above-described compounds of this invention are sometimes obtained as hydrates and they are also within the scope of this invention. In the present specification, these hydrates will be described as coming within the scope of the compounds of formula [I] in the free form, other than the salts of the compounds of formula [I].

Relatively similar compound to the compounds of this invention are disclosed in British Pat. Specification No. 1,129,358 (published Oct. 2, 1968) and German Offenlegungschrift No. 2,143,369 (published Mar. 9, 1972) as antibacterial agents.

We have made an attempt to prepare antibacterial agents which are more useful than these known compounds, and found that by introducing a piperazine into Process l The compounds of formula [I] are prepared by reacting compounds (a) of the following formula wherein X is a halogen atom, a lower alkylthio group, a lower alkoxy group, and R and R are the same as defined above;

with compounds (b) of the following formula wherein R is the same as defined above.

The reaction in this process l) is performed by heating the compounds (a) and (b) at atmospheric pressure in a solvent, if desired, in the presence of a base such as sodium bicarbonate or triethylamine to give the compounds of formula [I] in good yield.

Where compounds (a) in which X is a halogen atom are used as starting material, it is preferred to perform the reaction in the presence of a base, as a dehydrohalogenating agent, such as sodium bicarbonate, sodium carbonate, potassium carbonate, or triethylamine. Usually, the compounds (a) and (b) are used in stoichiometric amounts. Furthermore, the compounds (b) may be used in excess to make them serve also as a dehydrohalogenating agent. The compounds (b) may be used in the form of hydrate or acid addition salts of, for example, hydrochloric acid. The preferred reaction temperature is in the range of 60C. to C.

The solvent used in this reaction should be selected according to the properties of the materials to be used. Examples of the solvent are alcohols such as ethanol or propanol, aromatic hydrocarbons such as benzene or toluene, halogenoalkanes such as dichloroethane or chloroform, ethers such as tetrahydrofuran, dioxane or diphenyl ether, acetonitrile, dimethyl sulfoxide, dimethylformamide, and water. They may be used either alone or in mixture.

Process (2) Of the compounds of formula [I], the following com- "a -fw C COOR e (300R -N N N /L -N/J wherein R,, R and R are the same as defined above, to induce intramolecular cyclization.

The reaction in process (2) is performed by heating the compounds (c) directly or in a high-boiling solvent, such as diphenyl ether, o-dichlorobenzene, diphenylene oxide, dibutyl phthalate, or mixtures of these. The suitable heating temperature is 140 to 260C.

It is also possible to perform the cyclization reaction in the presence of a conventional cyclization agent such as polyphosphoric acid, a polyphosphoric acid alkyl ester, concentrated sulfuric acid or phosphorus pentoxide. Where polyphosphoric acid, polyphosphoric acid alkyl ester or phosphorus pentoxide is used as the cyclization agent, the reaction is generally carried out in a solvent such as benzene, dioxane or dimethylformamide. When concentrated sulfuric acid is used, the reaction is generally carried out in a solvent such as acetic anhydride or acetic acid. Of course, depending upon the properties of the cyclization agent, it can be made to serve also as the solvent. If the cyclization agent is used, the reaction is carried out at relatively low temperatures.

Process (3) coon,

wherein R, and R are the same as defined above, and R is an alkyl group having 1 to 4 carbon atoms, and

alkyl group having 2 to 4 carbon atoms substituted by hydroxy or halogen an allyl or a benzyl group;

are obtained by reacting compounds (d) (the compound of formula (I) in which R, is a hydrogen atom),

wherein R, and R are the same as defined above, with an alkylating agent corresponding to R Known alkylating agents can be used. Specific examples include alkyl halides such as methyl iodide, ethyl iodide, allyl bromide, benzyl chloride, 1,2- dibromoethane, ethylene chlorohydrin or ethylene bromohydrin, and lower alkyl esters such as dimethyl sulfate, diethyl sulfate, methyl p-toluenesulfonate, or triethyl phosphate.

The reaction in the process (3) is generally carried out by reacting the compound (d) with a stoichiometric amount of the alkylating agent in an inert solvent at an elevated temperature. If desired, the alkylating agent may be used in excess. The solvent may be either nonaqueous or hydrous. Examples of the solvent are ethanol, dioxane, dimethylformamide, dimethyl sulfoxide and water. The reaction is promoted by adding an acid acceptor, for example, a base such as an alkali carbonate, an alkali hydroxide, an alkali metal alkoxide, sodium hydride, triethylamine, or benzyltrimethyl ammonium hydroxide. Where the alkylating agent is made to act in a hydrous solvent, the carboxylic acid ester portion sometimes undergoes hydrolysis depending upon the reaction conditions, and thus is converted to a free carboxylic acid. Furthermore, when compounds of formula (d) in which R, is a hydrogen atom are alkylated, N-alkylated products at the 4-position of the piperazine nucleus can be obtained together with N-alkylated products at the 8-position of the pyrido[2,3- d]pyrimidine nucleus. Accordingly, the desired products can be obtained by suitably choosing the starting material, solvent and alkylating agent.

Where the product of the formula [I-b] is a compound in which R is a hydroxyalkyl group, it may be further halogenated with a halogenating agent such as thionyl chloride or phosphorus oxychloride to convert the hydroxyalkyl group to a halogenoalkyl group.

Process (4) Compounds of formula [I-b] can also be obtained by heating compounds of formula (e) below 9 COOR tetrahydrofuran, 1,2-dimethoxyethane, dimethyleneglycol dimethyl ether or diphenyl ether), or aromatic hydrocarbons (such as benzene or toluene). The reaction is promoted by adding a-catalyst such as a Lewis acid (such as boron trifluoride, or aluminum chloride) or a protonic acid (such as toluenesulfonic acid, sulfuric acid, hydrochloric acid or phosphoric acid). The heating temperature is 40 to 250C.

By reacting the compound (e) with the abovedescribed alkylating agent in at least a stoichiometric amount in a solvent, the compound [l-b] can be obtained. Examples of the solvent are water, dimethylformamide, and dimethyl sulfoxide in addition to the above-exemplified solvents. When alkylating agents are liquid alkyl halides or alkyl phosphates, they may be used concurrently as solvents.

Process (5 Compounds of formula [I] wherein R is a hydrogen atom, that is, compounds of formula [I-c] below H coo-H Y wherein R, and R are the same as defined above, can be obtained by hydrolyzing compounds of formula [I] wherein R is an alkyl group having 1 to 6 carbon atoms, that is, compounds of formula (h) below wherein P,, R; and R are the same as defined above.

The hydrolysis reaction in the process is carried out by contacting the compound (h) with water. Generally, in order to promote the reaction, it is performed in the presence of a catalyst such as an acid or base.

Examples of the acid are inorganic acids such as hydrochloric acid, hydrobromic acid, hydroiodic acid, sulfuric acid or phosphoric acid, and organic acids such as acetic acid, oxalic acid or toluenesulfonic acid.

Examples of the base are alkali metal hydroxides such as sodium hydroxide or barium hydroxide, alkali metal carbonates such as sodium carbonate or potassium carbonate, and sodium acetate.

This reaction may also be performed by directly heating the material in the presence of the above acid, and then adding water. The solvent is usually water, but depending upon the properties of the material, a hydrous solvent such as ethanol, dioxane, ethyleneglycol dimethyl ether, benzene or acetic acid may be used. The reaction temperature may be room temperature, but usually 50 to 200C., preferably 70 to 120C. Where R, in the compound (h) isa formyl or trifiuoroacetyl group, R, is converted to a hydrogen atom by being hydrolyzed together with the ester portion of this compound.

Process ,6l

Of the compounds of formula(-l), those in which R, is a hydrogen atom, that is, compounds of formula [l-d] below rt-ii [143 wherein R and R are the same as defined above, can be obtained by hydrolyzing or hydrogenolyzing compounds of formula (i) below C [CUR bonicacid residues as described above.

The derivatives of the alcoholic hydroxy] group as Z include, for example, acyloxy groups such as acetyloxy or ethoxycarbonyloxy; aryl sulfonyloxy groups such as tosyloxy or benzenesulfonyloxy, or lower alkylsulfonyloxy groups such as methanesulfonyloxy or ethanesulfonyloxy; or S-aryldithiocarbonyloxy groups such as S-phenyldithiocarbonyl0xy, or lower alkyldithiocarbonyloxy group such as S-methyldithiocarbonyloxy or S-ethyldithiocarbonyloxy groups.

Specific examples of the group that can form a tertiary or quaternary amine together with the residue are 9 and -l\ (UEI The hydrolysis reaction in the process 6) is generally carried out by reacting the compound (i) with a mineral acid or an alkali hydroxide. At this time, the ester portion is also hydrolyzed to form a free carboxylic acid. Where R, is a formyl, trifluoroacetyl or trityl group, it is split off under mild hydrolysis conditions without affecting the other functional groups. This reaction is carried out at 20 to C.

The hydrogenolysis reaction in the process (6) is carried out by hydrogenating the compound (i) using, for example, a hydrogen gas stream in a solvent in the presence of a catalyst such as platinum, palladium or Raney nickel, or by hydrogenolyzing the compound (i) with metallic sodium in liquid ammonia. The above catalytic hydrogenolysis reaction proceeds at room temperature. If desired, however, it may be carried out at an elevated temperature up to 60C Suitable solvents are ethyleneglycol, 'dioxane, dimethylformamide, ethanol, and acetic acid. Especially when R, is a benzyl, trityl or tosyl group, such a group can be split off with metallic sodium in liquid ammonia.

7 Process (7) Of the compounds of formula (1), those in which R,

is a vinyl group, that is, compounds of the formula [l-e] below wherein R, and R are the same as defined above, can be obtained by heating compounds (j) below wherein R, and R are the same as defined above; and Y and Z are different from each other, and each represent a hydrogen atom, a halogen atom, a lower alkoxy group, a benzyloxy group, an alcoholic hydroxy group or its derivative, or a group that can form a tertiary or quaternary amine together with the residue, with the proviso that either Y or Z is always a hydrogen atom.

The derivatives of the alcoholic hydroxy groups as Y and Z include, for example, acyloxy groups such as acetyloxy or ethoxycarbonyloxy; arylsulfonyloxy groups such as tosyloxy or benzenesulfonyloxy, or lower alkylsulfonyloxy groups such as methanesulfonyloxy or ethanesulfonyloxy; or S-aryldithiocarbonyloxy groups such as S-tolyldithiocarbonyloxy or S-phenyldithiocarbonyloxy, or lower alkyldithiocarbonyloxy such as S-methyldithiocarbonyloxy or S-ethyldithiocarbonyloxy groups.

Specific examples of the group as Y and Z that can form a tertiary or quaternary amine with the residue are The reaction in process (7) is carried out by simply heating the compound (j) or heating it in the presence of a catalyst such as an acidic substance, an acid anhydride or a base. Examples of the catalyst are ordinary acids such as hydrochloric acid, sulfuric acid, polyphosphoric acid, phosphoric anhydride, formic acid, acetic acid, toluenesulfonic acid, or potassium bicarbonate, Lewis acids such as thionyl chloride, phosphorus oxychloride, boron trifluoride or zinc chloride, alkali hydroxides, alkali carbonates, metal hydrides such as sodium hydride, alkali metal alkoxide such as sodium ethylate, sodium methoxide or potassium tert.- butoxide, pyridine, collidine, benzyltrimethylammonium hydroxide, acetic anhydride, phthalic anhydride, silver oxide, iodine, and tert.-butyl lithium.

The reaction temperature is usually 50 to 270C. The reaction proceeds in the absence of solvent, but

preferably, it is carried out in a solvent. Examples of the solvents are water, alcohol, acetic acid, dimethylformamide, dimethyl sulfoxide, ether, benzene, dioxane, tetrahydrofuran, and pyridine.

In this reaction, depending upon the nature of R, and/or R of the starting compound (j) and the reaction conditions, R, and/or R of the final product [I-e] may sometimes be replaced with a hydrogen atom.

The starting compound (a) used in process (1) is a known compound disclosed in German Offenlegungschrift No. 2,143,369 described above. The starting compound (b) is a known compound and can be obtained by known methods.

The starting compound (c) used in process (2) is obtained by reacting the corresponding 2-( l-piperazinyl)- o-aminopyrimidine and alkoxymethylenemalonate in accordance with the method disclosed in British Pat. Specification No. 1,129,358.

The compound (e) used in process (4) is a novel compound which is obtained by heating a compound (f) below wherein R, and R are the same as defined above; together with an excess of a halogenating agent such as phosphorus oxychloride in a solvent such as benzene through intramolecular cyclization to produce a compound of the following formula (g) below wherein R, and R are the same as described above, and X is a halogen atom; and then heating this compound with an alkali metal alkoxide in a solvent such as dimethyleneglycol dimethyl ether, dioxane, benzene or a lower alcohol, or with a lower alcohol in the presence of a base such as an alkali metal tert.-butoxide or trimethylbenzylammonium hydroxide.

The starting compound (i) used in the process (6) partly covers the compound of formula [I] in accordance with this invention, and can be prepared in the same manner as in process (1) or by reacting the compound (d) with an alkylating agent in the same manner as in the process (3).

The starting material (j) used in the process (7) is a novel compound, and can be prepared by reacting the starting compound (d) used in the process (3) with a halide of the formula CH- ,ZCHY-halogen (k) wherein Y and Z are the same as defined above; in the same way as described in the process (3).

The compound ((1) used as the starting compound in the process (3) and the compound (h) used as the starting compound in the process (5) are part of the compounds [I] of this invention, and can be prepared by any of the suitable methods described above.

The compounds of the present invention prepared in the above process can be isolated and purified by usual methods. The compounds [I] can be obtained in the. free state or in the form of salts depending upon the selection of the starting materials and the reaction conditions. Furthermore, the compounds [I] can be converted to pharmaceutically acceptable amine salts or carboxylic acid salts by treatment with acid or alkali, or vice versa. The acid may be a variety of organic and inorganic acids, examples of which are hydrochloric acid, acetic acid, lactic acid, succinic acid, oxalic acid and methanesulfonic acid.

The antibacterial activities of the typical compounds of this invention are shown in Tables I to V together with those of the compounds disclosed in the aforesaid 15 British Patent or German Patent.

In the Tables [I to IV, the ED and LD values were calculated in accordance with the Behrens-kaerber method [Arch. Exp. Path. Pharm., 162, 480 (1931)]. The compound numbers are those described in the Examples and compounds PA and AT-6l6 are as follows: Compound PA:

5,8-Dihydro-8-ethyl-2-pyrrolidino-5-oxopyrido [2,3- d]pyrimidine-6-carboxylic acid, which is the most valuable compound disclosed in the British Patent. Compound AT-6l6:

5,8-Dihydro-8-ethyl-2-(3-hydroxy-pyrrolidino)-5- oxopyrido[2,3-d]pyrimidine-6-carboxylic acid, which is the most valuable compound disclosed in the German Patent.

1. In vitro antibacterial activity against 3 strains of bacteria O M r at. 11., I N I i z i u -1 is n :1 1 I Table I MIC (pg/ml) Compound R R R Staphylococcus Escherichia Pseudomonas aureus coli aeruginosa Terajima K-12 Tsuchijima 1 H C H H 30 1 l 2 H nC;,H H 100 3 30 4 OH CH;,CHCH., C H H 30 3 100 11* H C H H 30 3 1O 17 ch 0 CH c,H H 3 100 21 C H C H H 1 100 33 H CH H 100 3 10 38 CH CCH C I-I H 10 3 100 H CH =CHCH H 10 3O 54* H CH =CH H 100 3 3 63* H ClCH CH H 30 3 30 PA 10 l 100 AT-6l6 30 1 100 *hydrochloride The minimum inhibitory concentration (MIC) was determined by the well known Inoculum: 1 drop of 1 10 dilution of an overnight broth culture per tube Incubation temperature and time: 37C for 48 hours 2 In vivo efficacy against systemic infection with Pseudomonas aeruginosa in mice Table II Compound Dose (mg/kg) ED No. Route 200 100 50 25 12.5 6.3 3.1 (mgl/kg) po 8/8 4/8 0/8 100 2 ip 8/8 35.4

po 5/8 2OO 11* ip x/s 17.7

po 8/8 7/8 100 21 ip 4/8 0/8 100 po 4/8 200 33 ip 8/8 17.7 5O ip 8/8 7/8 l/8 35 63* ip 8/8 8/8 17.7 PA ip 0/8 100 The numerical figures in the table show the number of the survival/the total number. /8 means that all of 8 mice died. 8/8 means that all 8 mice survived: The survival rate of nontreatcd control was 0/8. Experimental conditions:

Organism: Pseudomonas aeruginosa No. 12

Mice: male mice (ddY-S) weighing 20 g approximately infection: intraperitoneal infection with 50 to 100 LD of a bacterial suspension in 4% gastric mucin (about 5 X cells/mouse) Medication: twice, about 5 minutes and 6 hours after infection Drug: an alkaline solution for parenteral administration and a suspension in 0.2% CMC for oral administration Observation of mortality: 7 days i.p.: intraperitoneal administration p.o.: oral administration 3) In vivo efficacy against systemic infection with Salmonella typhimurium in mice Experimental conditions:

Medium: Kirchner medium containing 0.2% bovine Table III Com- Dose (mg/kg) ED pound No. Route 100 50 12.5 6.3 (mg/kg) 1 ip 8/8 8/8 4/8 6.3 pc 8/8 8/8 4/8 0/8 12.5 4 ip 8/8 35.4 po 8/8 35.4 11* p0 8/8 35.4 21 ip s/s 17.7 po 8/8 17.7 33 ip 7/8 4/8 1/8 12.5 38 p0 8/8 6/8 0/8 21.0 54* po 8/8 6/8 2/8 17.7 PA ip 9/10 5/10 3/10 O/lO 43.5 po 10/10 4/10 3/10 0/10 46.7

The numerical figures in the table show the number of the survival/the total number. 0/8 means that all of8 mice died. 8/8 means that all 8 mice survived. The survival rate of nontreated control was 0/8. Experimental conditions.

Organism: Salmonella typhimurium S-9 Mice: male mice (ddY-S) weighing 20 g approximately Infection: lntraperitoneal infection with to 100 LD of a bacterial suspension in nutrient broth (about 10 cells/mouse) Medication: twice a day for 4 days from the day of infection. Drug: an alkaline solution for parenteral administration and suspension in 0.2% CMC for oral administration Observation: 14 days i.e.: intraperitoneal administration p.o.: oral administration 4) Antituberculous activity in vitro 50 albumin, pH 7.0 (3ml/tube) Table IV Mycobacterium tuberculosis H,-,-,R,. Com- R R R H R Kurono resistant* pound *lNH. PAS. SM-rcsistant strain The minimum inhibitory concentration (MIC: ,ug/ml) was determined by the well known serial dilution method.

lnoculum: 1 drop of 1:10 dilution of a culture in Modified Kirchner medium for 2 weeks (OD=O.3) per tube Incubation temp. and time: 37C for 3 weeks Dose (mg/kg) LD Compound Route 4000 2000 1000 500 (mg/kg) The numerical figures in the table show the number of survival/the total number. 0/6 means that all of 6 mice died and 6/6 means that all of mice survived.

The compound was in an alkaline solution for intravenous administration and a suspension containing 0.2% CMC for oral administration, and was administered to male mice (ddY-S) weighing 20 g approximately. After 7 days, the incidence of death was recorded and LD value was estimated.

i.v.: intravenous administration p.02 oral administration A clinical dosage of the compound [1] depends on body weight, age and administration route but it is generally in the range of 100 mg g/day, preferably of 200 mg3g/day.

The compounds [I]may be used as medicines, for example, in the form of pharmaceutical preparations containing the compound in admixture with organic or inorganic, solid or liquid pharmaceutical adjuvants suitable for peroral, parenteral, enteral or local administration. Pharmaceutically acceptable adjuvants are substances that do not react with the compounds, for example, water, gelatin, lactose, starch, cellulose, preferably microcrystalline cellulose, carboxymethyl cellulose, methyl cellulose, sorbitol, magnesium stearate, talc, vegetable oils, benzyl alcohol, gums, propylene glycol, polyalkylene glycols, methylparaben and other known medicinal adjuvants. The pharmaceutical preparations may be, for example, powders, tablets, ointments, suppositories, creams or capsules, or in liquid form as solutions, suspensions or emulsions. They may be sterilized and/or contain assistants such as preserving, stabilizing, wetting or emulsifying agents, salts for regulating the osmotic pressure or buffers. They may further contain other therapeutically valuable substances. The preparations are prepared by conventional methods.

Example A 5,8-dihydro-8-ethyl-2-( l-piperazinyl)-5-oxopyrido[2,3- 250 g d]pyrimidine--carboxylic acid Starch 54 g Calcium carboxymethyl cellulose 40 g Microcrystalline cellulose 50 g Magnesium stearate 6 g The above components are blended, granulated and made into tablets in a conventional manner. Thus,

1000 tablets each weighing 400 mg were formed.

The above components were blended and granulated and filled into 1,000 capsules in accordance with conventional methods.

Example C 5,8-dihydro-8-ethyl-2-(l-piperazinyl)-5- 5 g oxopyrido[2,3-d1pyrimidine--carboxylic acid hydrochloride Sorbitol 30 g Sugar 40 g Methylparaben Small amount Sodium carboxymethyl cellulose Small amount Flavor Small amount Water to make ml The following Examples illustrate the preparation of the compounds of the present invention. In all of the Examples, percentages are by weight unless otherwise specified.

Examples 1 to 14 illustrate the preparation of the compounds of this invention in accordance with the process (1).

EXAMPLE 1 5 ,8-Dihydro-8-ethyl-2-( l-piperazinyl )-5-oxopyrido- [2,3-d]pyrimidine-o-carboxylic acid (compound 1) A mixture containing 1.33 g of 5,8-dihydro-8-ethyl- 2-methylthio-5-oxopyrido[2,3-djpyrimidine-6- carboxylic acid, 1.94 g of piperazine hexahydrate and 20 ml. of dimethyl sulfoxide was heated at 1 10C for 1 hour with stirring. The separated solid was collected by filtration, washed with ethanol, and then dried at such a temperature that did not rise above 50C to give 1.57 g of the trihydrate of the product as nearly colorless needles, mp. 253 255C.

Analysis calcd. for C l-l O N .3H O C, 47.05; H, 6.49; N, 19.62; H O, 15.12. Found: C, 46.87; H, 6.41; N, 19.54; H O, 15.1.

The trihydrate was further dried at C to give 1.31 g of the anhydrous product, m.p. 253 255C.

Analysis calcd. for C T-1 0 19 C, 55,43; H, 5.65; N, 23.09. Found C, 55.48; H, 5.74; N, 22.85.

EXAMPLE 2 5,8-Dihydro-8-ethyl-2-(4-methyi- 1 -piperazinyl)-5- oxopyrido-(2,3-d)pyrimidine-6-carboxylic acid (compound 3).

A mixture containing 1.33 g of 5,8-dihydro8-ethyl- 2-methylthio-5-oxopyrido[2,3-d]pyrimidine-6- carboxylic acid, 1.30 g of 4-rnethylpiperazine, and 20 ml of dimethyl sulfoxide was heated at l 10C for 1 hour with stirring. The separated solid was collected by filtration, washed with ethanol, and recrystallized from dimethylformamide to give 1.86 g of the product, as nearly colorless needles, mp. 232 233C.

EXAMPLE 3 5 ,8-Dihydro8-ethyl- 2-[4-(2-hydroxy-n-propyl)-1- piperazinyl]-5-oxopyrido[2,3-d]pyrimidine-6- carboxylic acid (compound 4) Following the procedure described in Example 2 using in place of 4-methyl piperazine 1.44 g of 4(2- hydroxy-n-propyl)piperazine, there is obtained 1.40 g of the product, as colorless needles, mp. 214 216C.

EXAMPLE 4 ,8-Dihydro-8-ethyl-2-(4-phenyll -piperazinyl)-5- oxopyrido[2,3-d]pyrimidine-6-carboxylic acid (compound 6) Following the procedure described in Example 2 using in place of 4-methyl piperazine 1.62 g of 4-phenylpiperazine, there is obtained 1.50 g of the product, as yellowish orange needles, m.p. 247 248C.

EXAMPLE 5 2-(4-Benzyl-1-piperazinyl)-5,8-dihydro-8-ethyl-5- oxopyrido[2,3-d]pyrimidine-6-carboxylic acid (compound 7) Following the procedure described in Example 2 using in place of 4-methyl piperazine 1.75 g of 4-benzylpiperazine, there is obtained 1.40 g of the product, as colorless scales, m.p. 204 206C.

EXAMPLE 7 The following compounds were prepared in the same way as in Example 2.

EXAMPLE 8 The following compounds were prepared in the same way as in Example 2.

5,8-Dihydro-2-( 1 -piperaziny1)-8-n-propy1-5- oxopyrido-[2,3-d]pyrimidine-6-carboxylic acid (compound 2) A mixture containing 1.40 g of 5,8-dihyd1'o-2- methylthio-S-n-propyl-S -oxopyrido[ 2 3-d pyrimidine- 6-carboxylic acid, 2.94 g of piperazine hexahydrate, and 20 ml of dimethylsulfoxide was heated at 110C for 1.5 hours. The precipitate was collected, washed with ethanol, and then recrystallized from water to yield 1.40 g of the product, as colorless nee-.

dles, m.p. 259 261C.

EXAMPLE l ,8-Dihydro-2-(4-methyl-1-piperazinyl)-8-n-propyl-5- oxopyrido[2,3-d]pyrimidine-6-carboxylic acid (compound 26) Following the procedure described in Example 9 using in place of piperazine hexahydrate a molar equivalent quantity of 4-methylpiperazine, there is obtained the product, m.p. 254 257C.

EXAMPLE 1 l 5 ,8-Dihydro-8-ethyl-5-oxo-2-( l-piperazinyl)-pyrido- [2,3]pyrimidine-6-carboxylic acid (compound 1) A mixture containing 1.0 g of 5,8dihydro-8-ethyl-2- methoxy-5-oxopyrido[2,3-d]pyrimidine-6-carboxylic acid 1.6 g of piperazine hexahydrate and 50 ml of dimethyl sulfoxide was heated at 100 100C for 1.5 hours. After removal of dimethyl sulfoxide by distillation under reduced pressure, the residual solid was recrystallized from dimethylformamide to give 1.0 g of the product, as colorless needles, m.p. 253 255C.

EXAMPLE l2 5,8-Dihydro-8-(2-hydroxyethyl)-2-(4-methyl-1- piperazinyl)-5-oxopyrido[2,3-d]pyrimidine-6- carboxylic acid (compound 31) Following the procedure described in Example 11, there is obtained the product, m.p. 232.5 233.5.

EXAMPLE 13 Ethyl 2-( 4-acetyll -piperazinyl )-5 ,8-dihydro-8-ethyl-5- oxopyrido[2,3-d]pyrimidine-6-carboxylate (compound 42).

A mixture containing 1.0 g of ethyl 2-chloro-5,8- dihydro-8-ethyl-5-oxopyrido[2,3-d]pyrimidine-6- carboxylate, 0.60 g of sodium bicarbonate, 20 ml of dimethyl sulfoxide, and 0.60 g of l-acetylpiperazine was heated at 120C for 1.5 hours with stirring. The dimethylsulfoxide was distilled off in vacuo and the residue was taken up in chloroform. The chloroform solution was washed with water, dried over anhydrous magnesium sulfate, and concentrated to dryness. The residual solid was recrystallized from a mixture of n-hexane and acetone to yield 1.21 of the product, m.p. 208 210C with decomposition.

EXAMPLE l4 5 ,8-Dihydro-2-( l-piperazinyl)-8-vinyl-5- oxopyrido[2,3-d]pyrimidine-6-carboxylic acid hydrochloride (compound 54) To a mixture containing 1.2 g of piperazine hexahydrate and 6 ml. of dimethylformamide heated at 80C was added a solution of ethyl 5,8-dihydro-2- methylthio-8-vinyl-5-oxopyrido[2,3-d]pyrimidine-6- carboxylate (0.47 g) in 6 ml of dimethylformamide. The reaction mixture was allowed to react at the same temperature for 2.5 hours with stirring. After removal of the solvent under reduced pressure 30 ml of 15% hydrochloric acid solution was added to the reaction mixture, which was then heated in a steam bath for 30 minutes. The solid that precipitated was collected, and dissolved in 30 ml of water. The resulting aqueous solution was treated with decolorizing charcoal followed by filtration. Addition of 2 ml of concentrated hydrochloric acid to the filtrate gave a solid on cooling, which was collected and recrystallized from diluted aqueous ethanol to yield 0.47 g of the product as colorless prisms, m.p. 298 301 C with decomposition.

Examples 15 to 19 illustrate the preparation of the salts of the compounds of this invention.

EXAMPLE 15 Potassium 5 ,8-dihydro-8-ethyl-2-( l-piperazinyl)-5- oxopyrido[2,3-d]pyrimidine-6-carboxylate (compound 32) To a solution of potassium carbonate (2.76 g) in 60 ml of water was added 6.06 g of 5,8-dihydro-8-ethyl-2- 1-piperazinyl)-5-oxopyrido[2,3-d]pyrimidine-6- carboxylic acid. The resulting mixture was heated on a steam bath until it became a clear solution. Ethanol was added to the solution, and the mixture was then kept below room temperature by external cooling to yield the precipitate, which was collected and washed with ethanol. There is obtained 4.2 g of the product m.p. above 300C.

EXAMPLE 16 EXAMPLE l7 5,8-Dihydro-8-n-propyl-2-( l-piperazinyl)-5- oxopyrido[2,3-d]pyrimidine-6-carboxylic acid hydrochloride (compound 28) Following the procedure described in Example 16, there is obtained the product, m.p. 294 295C with decomposition.

EXAMPLE 18 5 ,8-Dihydro-8-ethyl-2-( l-piperazinyl)-5- oxopyrido[2,3-dlpyrimidine-6-carboxylic acid acetate (compound 12) To a stirred suspension containing 0.30 g of 5,8- dihydro-8-ethyl-2-( l-piperazinyl)-5 -oxopyrido[2,3- d]pyrimidine-6-carboxylic acid and 20 ml of an absolute ethanol was added 2 ml. of glacial acetic acid at room temperature. The reaction mixture was stirred for an additional two hours. The resulting precipitate was collected, and washed with ethanol to yield 0.35 g of the product, as colorless needles, m.p. 257 258C.

EXAMPLE 19 The following salt were prepared in the same way as in Example 18.

.8-Dihydro-8-ethyl-2-( l-piperazinyl)-5- oxopyridol2,3-d]pyrimidine-6-carboxylic acid lactate (compound 13): mp. 230 235C.

5 ,8-Dihydro-8-ethyl-2-( l-piperazinyl)-5-oxopyrido2,3- d]pyrimidine-6-carboxylic acid succinate (compound 14): m.p. 202 204C.

5 ,8-Dihydro-8-ethyl-2-( 1 -piperazinyl)-5- oxopyrido[2,3-d]pyrimidine-6-carboxylic acid oxalate (compound 15): m.p. 261 263C.

5 ,8-Dihydro-8-ethyl-2( l-piperazinyl)-5- oxopyrido[2,3-d]pyrimidine-6-carboxylic acid methanesulfonate (compound 16): m.p. 294 295C. (dec.)

Examples 20 to 25 illustrate the preparation of the compounds of this invention by the process 2).

EXAMPLE 20 Ethyl 2-( 4-acetyll -piperazinyl)-5 ,8-dihydro-5- oxopyrido[2,3-dlpyrimidine-6-carboxylate (compound 59) To 16 ml of diphenyl ether heated at 250 255C was added with stirring 2.0 g of diethyl N-[2-(4-acetyll-piperazinyl )-4-pyrimidinyl]- aminomethylenemalonate, gentle refluxing was continued for 10 minutes, and then the mixture allowed to cool to room temperature. To the mixture was added 12 ml of n-hexane and the resulting precipitate was collected, washed with ethanol, and recrystallized from ethanol to yield 1.52 g of the product, m.p. 300 302C with decomposition.

EXAMPLE 2] The following compounds were prepared in the same way as in Example 20.

5 ,8-dihydro-8-ethyl-2-( 4-methyll -piperazinyl )-5- oxopyrido[2,3-d]pyrimidine-6-carboxylate (compound 22) A mixture containing 1.0 g of diethyl N-ethyl-N-[2- (4-methyll -piperazinyl )-4- pyrimidinyl]aminomethylene malonate and 6.0 g of polyphosphoric acid was heated at 140C for 20 minutes, and then poured into ice-water. The resulting mixture was made alkaline with 28% aqueous ammonia and extracted with chloroform. The extract was washed with water, and dried over anhydrous magnesium sulfate, and the solvent was removed by distillation to give a crude product which was recrystallized from water to give 0.72 g of the product, m.p. 146 147C.

EXAMPLE 23 Ethyl 2-(4-benzyll -piperazinyl)-5,8-d1nydro-o-ethyl-5- oxopyrido[2,3-d]pyrimidine-6-carboxylate (compound 55) Following the procedure described in Example 22, there is obtained the product, m.p. 151 153C.

EXAMPLE 24 Ethyl 5,8-dihydro-8-ethyl-2-( 1-piperazinyl)-5- oxopyrido[2,3]pyrimidine--carboxylate (compound 56 Diethyl N-ethyl-N-[2-( l-piperazinyl)-4-pyrimidinyl]- aminomethylenemalonate (1.0 g) was heated at 250C for 30 minutes and the resulting solid was recrystallized from ethanol to give 0.73 g of the product, m.p. 156 158C.

EXAMPLE 25 Ethyl 5 ,8-dihydro-2-(4-methyll -piperazinyl)-5- oxopyrido[2,3-d]pyrimidine-6-carboxylate (compound EXAMPLE 26 Ethyl 2-(4-acetyll -piperazinyl )-5 ,8-dihydro-8-ethyl-5- oxopyrido[2,3-d]pyrimidine-6-carboxylate (compound To a suspension of ethyl 2(4-acetyl-l-piperazinyl)- 5,8-dihydro-5-oxopyrido[2,3-d]pyrimidine-6- carboxylate (4.0 g), and 6.0 g of potassium carbonate in ml of 50% aqueous ethanol was added with stirring a total of 5.5 ml diethyl sulfate in three portions and the mixture was allowed to react for 2 hours at room temperature.

The reaction product was extracted with chloroform, and the extract dried over anhydrous magnesium sulfate, followed by evaporation of the solvent to leave a crystalline residue, to which n-hexane was added. The crystals were collected and recrystallized from a mixture of n-hexane and acetone to give 3.4 g of the product, m.p. 208 210C with decomposition.

EXAMPLE 27 2-(4-Acetyl-1-piperazinyl)-5,8-dihydro-8-ethyl-5- oxopyrido[2,3-d]pyrimidine-6-carboxylic acid (compound 10) To a solution of 0.45 g of 2(4-acetyl-l-piperazinyl)- 21 5,8-dihydro--oxopyrido[2,3-d]pyrimidine-6- carboxylic acid in 30 ml of sodium carbonate was added two 0.5 ml portions of diethyl sulfate with stirring at room temperature. After the completion of the reaction the mixture was neutralized with acetic acid. The precipitate resulted was collected and recrystallized from dimethylformamide to yield 0.4 g of the product, m.p. 298 300C.

EXAMPLE 28 2-(1-piperazinyl)- and 2-(4-ethyl-1-piperazinyl)-5 ,8-dihydro-8-ethyl-5- oxopyrido[2,3-dlpyrimidine-6-carboxylic acids (compound 1 and 21) To a solution of 1.5 g of 5,8-dihyro-2-(lpiperazinyl)-5-oxopyrido[2,3-dlpyrimidine-6- carboxylic acid in 60 ml of a aqueous solution of sodium carbonate was added three 10 ml portions of diethyl sulfate. After completion of the reaction, the resulting mixture was neutralized with acetic acid. The precipitate was collected and recrystallized from dimethylformamide to give 0.8 g of 2-(1-piperazinyl)- 5,8-dihydro-8-ethyl-5-oxopyrido[2,3-d]pyrimidine-6- carboxylic acid (compound 1) mp. 253 255C. Concentration of the mother liquor to about a half volume gave another solid which was further recrystallized from the same solvent to give 0.6 g of 2-(4-ethy1-1- piperazinyl)-5,8-dihydro-8-ethyl-5-oxopyrido[2,3- d]pyrimidine-6-carboxylic acid (compound 21), mp. 228 230C.

EXAMPLE 29 5 ,8-Dihydro-8-ethyl-2-(4-methyl-1 -piperazinyl)-5- oxopyrido[2,3-d]pyrimidine-6-carboxylic acid (compound '3) To a mixture containing 1.0 g of 5,8-dihydro-2-(4- methyl-1-piperazinyl)-5-oxopyrido[2,3-d]pyrimidine- 6-carboxylic acid, 1.0 of 65% sodium hydride, and 40 ml of dimethylformamide held at 60C, was added 1.0 ml of ethyl iodide. The resulting mixture was heated in a steam bath for 2.5 hours. Dimethylformamide was distilled off in vacuo, the residue dissolved in 10 ml of water, and the resulting solution neutralized with acetic acid. The precipitate was collected and recrystallized from ethanol to yield 0.72 g of the product, m.p. 232

EXAMPLE 3O Ethyl 2-(4-benzyl-l-piperaziny1)-5 ,8-dihydro-8-ethyl-5- oxopyrido[2,3-d]pyrimidine-6-carboxylate (compound 55) A mixture of 1.3 g of ethyl 2-(4-benzyl-1- piperazinyl)-5,8-dihydro-5-oxopyrido[2,3- d]pyrimidine-6-carboxylate, 5.0 ml of ethyl iodide, ml of a 12% aqueous solution of sodium carbonate, and 200 ml of dimethylformamide was heated at 95C for 3 hours. After removal of the solvent and an excess of the reagent by distillation in vacuo, the resulting residue was taken up in chloroform and filtered. The filtrate was concentrated to dryness to leave a solid which was collected and recrystallized from ethanol to give 1.0 g of the product, m.p. 15l- 153C EXAMPLE 31 8-Benzyl-5,8-dihydro-2-(4-methyl-1-piperazinyl)-5- oxopyrido[2,3-d]pyrimidine-6-carboxylic acid (compound 19) Example 32 The following compounds were prepared in the same way as in Example 26.

The following compounds were prepared in same way as in Example 27.

Com- R, R R m.p.C. pound 6 C H H 247 248 The following compounds were prepared in the same way as in Example 28.

The following compounds were prepared in the same way as Example 29.

Com RI R2" R3 m.p.C. pound 7 CH2 C2H5 H 204 206 17 cH o CH2- C H H 198 199 21 H C.,H,., H 228 230 39 CH -,O C H H 218 220 CH;,O

38 CH 5 F C-,H,, H 254 257 The following compounds were prepared in the same way as in Example 30 To a solution of 8.0 g of ethyl 5,8-dihydro-8-(2- hydroxyethyl)-2-(4-methyl-1-piperazinyl)-5- Com- R R2" R m.p.C. pound 58 CH2 C2H5 nC;,H 156.6 158.5

Example 33 oxopyrido-[2,3-d]pyrimidine-6-carboxylate in 80 ml of chloroform was added with stirring 6 ml of thionyl COCR chloride, the resulting mixture was allowed to react at N 5 room temperature for 30 minutes and then heated to l l refux for 2 hours. After removal of the solvent and an R N A7 N excess of the reagent, the residue was taken up in chlol 35 roform. The chloroform solution was washed with wa- 2 ter, dried and the solvent distilled off. The solid ob- The following compounds were prepared in the same tained was recrystallized from ethyl acetate to give 6.9 way as in Example 31. g of the product, m.p. 154 155C.

Com- Alkylating poun No. RI R2" R3 m.p.C. agent 26 CH nC;,H-, H 254 257 n-C -,H Br 31 CH;, HOCH2CH2 H 232.5 233.5 HOCHZCHZCI 37 CH;, CH2=CHCH2 H 256 258 CH =CHCH Br CH, C1CH CH H 226- 228 ClCH CH- Cl Example 34 Examples 36 to 42 illustrate the preparation of the Ethyl compounds of this invention by the process(4). 5 ,8-dihydro-8-(2-hydroxyethyl)-2-(4-methyl-1- i erazin l)-5-oxopyrido[2,3-d]pyrimidien-6 p p -c arboxy1ate (compound 68) Example 36 A mixture containing 5.0 g of ethyl 5,8-dihydro-2-(4- methyl-l-piperazinyl)-5-oxopyrido 2,3-d pyrimidine-6- carboxylate, 70 m1 of dimethylformamide, 0.90 g of Ethyl U 50% sodium hydride, and 3.8 g of ethylene chlorohy- -q y 2-t 'P P yU- drin was heated at 100C for 1 hour. Dimethylform- Oxopyndol23dlpynmldme''carboxylate (compound amide was distilled off in vacuo, and the residue taken 22) up in chloroform. The chloroform solution was washed with water, dried over anhydrous magnesium sulfate, and the solvent distilled off. The resulting solid was re- A mixture containing 1.0 g of ethyl 5-ethoxy-2-(4- crystallized from ethanol to yield 4.6 g of the product, methyl-1-piperazinyl)pyrido]2,3-d]pyrimidine-6- m.p. 197 199C. carboxylate and 5.0 ml of dimethylene glycol dimethyl ether was heated to reflux for 3 hours. The solvent was Example 35 removed by distillation in vacuo and the residual solid Ethyl was recrystallized from water to yield 0.72 g of the 8-( 2-chloroethyl )-5 ,8-dihydro-2-( 4-methyll piperazinyl )-5oxopyrido[ 2,3-d lpyrimidine-6- carboxylate (compound 69) product, m.p. 146 147C.

The starting materials used above were prepared as follows:

Ethyl -chloro-2-(4-methyll piperazinyl)pyrido[2,3-d1pyrimidine-6-carboxylate.

A mixture containing 30 g of diethyl N-[(4-methyl-1- piperazinyl)-4-pyrimidinyl]aminomethylene malonate and 150 ml of phosphorus oxychloride was heated at 95C for 5 hours. An excess of the reagent was removed in vacuo, the residue was made alkaline with 28% aqueous ammonia. The resulting mixture was extracted with chloroform, the extract washed with cold water, and dried over anhydrous magnesium sulfate. The solvent was distilled off to leave a solid which was recrystallized from acetone. There was obtained 23.5 g of the above product as yellow needless, m.p. 173 175C.

Ethyl 5-ethoxy-2-(4-methyl-lpiperazinyl)pyrido[2,3-dlpyrimidine-6-carboxylate.

A mixture containing 3.0 g of ethyl 5-chloro-2-(4- methyl-1-piperazinyl)pyrido[2,3-dlpyrimidine-- carboxylate, 0.7 g of sodium ethoxide, and 50 ml of absolute ethanol was heated to reflux for 2 hours. The ethanol was removed by distillation in vacuo, the residue was extracted with chloroform and the extract washed with water, and dried over anhydrous magnesium sulfate. After the solvent was distilled off the residue was crystallized from n-hexane to give 2.8 g of the product as pale yellow needles, m.p. 105 108C.

Example 37 Ethyl 5 ,8-dihydro-8-ethyl-2-( 4-methyll -piperazinyl )-5- oxopyrido[2,3-d1pyrimidine-6-carboxylate (compound 22).

a mixture containing 1.0 g of ethyl 5-ethoxy-2-(4- methyl-1-piperazinyl)pyrido[2,3-d1pyrimidine-6- carboxylate and 5.0 ml of ethyl iodide was heated to reflux for 1 hour. After ethyl iodide was recovered by distillation, the resulting solid was crystallized from water to give 0.69 g of the product, m.p. 146 147C.

Example 38 Ethyl 5,8-dihydro-8-ethyl-2-( l-piperazinyl)-5- oxopyrido[2,3-dlpyrimidine-6-carboxylate (compound 56) Following the procedure described in Example 36 using ethyl 5-ethoxy-2-(1-piperazinyl)pyrido[2,3-d]- pyrimidine-6-carboxylate, there is obtained the product, m.p. 156 158C.

Example 39 Ethyl 2-(4-acetyl-1-piperazinyl)-5 ,8-dihydro-8-ethyl-5- oxopyridol 2,3-d]pyrimidine-o-carboxylate (compound 42) Following the procedure described in Example 37 using ethyl 2-(4-acetyl-1-piperaziny1)-5- ethoxypyrido[2,3-d]pyrimidine-o-carboxylate with ethyl iodide, there is obtained the product, m.p. 208 210C with decomposition.

Example 40 Ethyl 2-(4-benzyl-l-piperazinyl)-5,8-dihydro-8-ethyl-5- oxopyrido[2,3-d]pyrimidinelo-carboxylate (compound 55) Following the procedure described in Example 37 26 using ethyl 2-( 4-benzyll -piperazinyl)-5- ethoxypyrido[2,3-d]pyrimidine-6-carboxylate with ethyl iodide, there is obtained the product, m.p. 151 153C.

Example 41 Ethyl 2-(4-acetyl1-piperazinyl)-8-(2-chloroethyl)-5,8- dihydro-5-oxopyrido[ 2,3-d]pyrimidine-6-carboxylate (compound 61 Ethyl v 2-( 4-acetyl- 1 -piperazinyl)-8-( 2-bromoethyl)-5 ,8- dihydro-5-oxopyrido[ 2 ,3-d]pyrimidine-6-carboxylate (compound 62) Following the procedure described above and using 1,2-dibromoethane in place of 1,2-dichloroethane, there is obtained the product, m.p. 202 204C.

Example 42 Ethyl 5 ,8-dihydro-8-( 2-hydroxyethyl)-2-(4-methyll piperazinyl)-5-oxopyrido[2,3-d]pyrimidine-6- carboxylate (compound 68) Following the procedure described in Example 37 using ethyl 2-(4-methyl-l-piperazinyl)-5-ethoxypyrido- [2,3-d]pyrimidine-6-carboxylate with ethylenebromohydrine, there is obtained the product, m.p. 197

Examples 43 to 51 illustrate the preparation of the compounds of this invention by the process(5).

Example 43 5 ,8-Dihydro-8-ethyl-2-( 1 -piperazinyl )-5-oxopyrido [2,3-dlpyrimidine-6-carboxylic acid (compound 1) Ethyl 5,8 -dihydro-8-ethy1-5-oxo-2-(lpiperazinyl) pyrido[2,3-d]pyrimidine-6-carboxylate (5.0 g) was dissolved in 30 ml of a 7% aqueous solution of sodium hydroxide by heating at C for 20 minutes. After cooling, the resulting solution was neutralized with acetic acid to yield a precipitate which was collected, and recrystallized from dimethylformamide. There is obtained 4.3 g of the product m.p. 253 255C.

Example 44 5 ,8-Dihydro-8-ethyl-2-( 4-methyl- 1 -piperazinyl )-5- oxopyrido[2,3-d]pyrimidine-6-carboxylic acid (compound 3) n-Propyl 5 ,8-dihydro-8-ethyl-2-(4-methy1- l piperazinyl)-5-oxopyrido[2,3-d]pyrimidine-6- carboxylate (4.5 g) was dissolved in 30 ml of a 10% aqueous solution of sodium carbonate by heating at C for 30 minutes.

After being cooled, the resulting solution was neutralized with acetic acid to give a precipitate which was collected and recrystallized from dimethylformamide.

27 There is obtained 3.8 g of the product, m.p. 232 233C.

28 Example 47 Using ethyl ester as a starting material, the following compounds were prepared in the same way as in Exam- Example 45 ple O 8-Benzyl-5,8-dihydro-2-(1-piperazinyl)-5-oxopyrido ,UOOH [2,3-dlpyrimidine-o-carboxylic acid (compound 33) l 1 i J Ethyl 8-benzyl-5,8-dihydro-2-( l-piperazinyl)-- R ,L N .2 oxopyrido[2,3-d]pyrimidine--carboxylate (1.5 g) was 10 l 1 f 1 disolved in ml of a 12% aqueous solution of sulfuric 2 acid by heating at 90C for 1 hour. The resulting solu- Rl R, m.p.C. tion was filtered to remove a small amount of the insol- Pound uble material and the filtrate was neutralized with 28% 34 H HOCHZCHP 249 l aqueous ammonia, to separate a sohd which was col- 5 50 H CH =CHCH 253 255 lected, washed with water, and recrystallized from di- CH (CII-L CHCH 2222:2252 methylformamide. There 1s obtained 1.1 g of the prod- 38 CH E 254 257 uct, m.p. 250 253C. cH.,- ClCH CH 226 22s Example 46 7 Example 48 Using n-propyl ester 88 a Sta ing te the fOlloW- using ethyl ester as a starting material, the following ing compounds were prepared in the same way as in compounds were prepared in the same way as in Exam- Example 44. ple 43.

3k 00011 T. .1 l I 1 4 w 11' l Com- RI R: m.p.C pound 26 CH- nC;,H 254 257 31 CH;, HOCH CH 232.5 233.5

7 Q CH2- C H 204 206 COOH 1 l Lu 1 I R -N N N "N Compound R R2 m.p.C

2 1-1 n c,,n, 259 261 17 c11 0 CH2 C2H 198 199 19 cu CH. 251 255 21 C2H5 C. ,H 228 w 29 Example 49 2-(4-Acetyl-1-piperazinyl)-5,8-dihydro-8-ethyl-5- oxopyrido(2,3-d)pyrimidine- 6-carboxylic acid (compound 10) Ethyl 2-(4-acetyll -piperazinyl )-5 ,S-dihydro-S-ethyl- 5-oxopyrido[2,3-d]pyrimidine-6-carboxylate (5.0 g) was dissolved in 35 ml of a aqueous solution of sodium carbonate by heating at 90C for 30 minutes. The resulting solution was filtered to remove the insoluble material, and the filtrate was neutralized with acetic acid to give a precipitate which was collected and recrystallized from a mixture of benzene and chloroform. There is obtained 4.1 g of the product, m.p. 298 300C.

Example 50 5 ,8-Dihydro-2-(4-methyll -piperazinyl )-8-vinyl-5- oxopyrido[2,3-dlpyrimidine-6-carboxylic acid (compound 52) 5,8-Dihydro-2-(4-methyl-l-piperazinyl)-8-vinyl-5- oxopyrido[2,3-d]pyrimidine 6-carboxylic acid, m.p. 233 234C, is obtained by hydrolysis of the corresponding ethyl ester as in Example 49.

Example 51 Example 52 5,8-Dihydro-8-ethyl-2-( l-piperazinyl)-5-oxopyrido- [2,3-d]-pyrimidine-6-carboxylic acid (compound 1) A. Z-Acetyl-l-piperazinyl)-5,8edihydro-8-ethyl-5- oxopyrido[2,3-d]-pyrimidine-6carboxylic acid (2.0 g) was dissolved in 40ml of a 10% aqueous solution of sodium hydroxide by heating at 90 9 5C for 1.5 hours. The resulting solution was treated with decolorizing charcoal and filtered. The filtrate was neutralized with acetic acid to give 1.6 g of the product as a pure state,

m.p. 253 255C.

B. Ethyl 2-(4-acetyl-1-piperazinyl)15,8-dihydro-8- ethyl-5-oxopyrido[2,3-dlpyrimidine-o-carboxylate (1.6 g) was dissolved in 30 ml of a 10% aqueous solution of sodium hydroxide by heating at 90 95C for 1 hour. Neutralization of the reaction mixture with acetic acid under cooling yielded a crude solid, which was recrystallized from dimethylformamide to give 1.1 g of the product as a pure state.

Example 53 5,8-Dihydro-8-ethyl-2-( l-piperazinyl)-5-oxopyrido [2,3-dlpyrimidine-6-carboxylic acid hydrochloride v (compound 11) .A mixture containing, 2.0 g of 5,8-dihydro-8-ethyl-2- (4-formyl-l-piperazinyl)-5-oxopyrido[2,3-d]- pyrimidine-6-carboxylic acid and 30 ml of 10% aqueous hydrochloric acid was heated at C for 1 hour. The reaction mixture was concentrated to dryness and addition of ethanol to the residue resulted in the separation of a solid, which has collected and washed with ethanol to yield 1.7 g of the product, m.p. above 300C.

Example 54 5 ,8-Dihydro-8-ethyl-2-( l-piperazinyl)-5-oxopyrido- [2,3-dlpyrimidine-6-carboxylic acid (compound 1) and 8-benzyl-5 ,8-dihydro-5-oxol2-( 1- piperazinyl)pyrido[2,3-d]-pyrimidine-6-carboxylic acid (compound 33) Following the procedure described in Example 52 (A) using 5 ,8-dihydro-2-(4-ethoxycarbonyl-1- piperazinyl)-8-ethyl-5-oxopyrido[2,3-d]pyrimidine-6- carboxylic acid or 2-(4-acetyl-l-piperazinyl)-8-benzyl- 5,8-dihydro-5-oxopyrido [2,3-d]pyrimidine-6- carboxylic acid, there is obtained, respectively, 5.8- dihydro-8-ethyl-2( l-piperazinyl)-5-oxopyrido[ 2,3- d]pyrimidine-6-carboxylic acid, m.p. 253 255C or 8-benzyl-5,8-dihydro-2-( l-piperazinyl)-5- oxopyrido[2,3-d]pyrimidine-6-carboxylic acid, m.p. 250 253C.

Example 55 5 ,8-Dihydro-8-n-propyl-2-( 1-piperazinyl)-5-oxopyrido [2,3-d]pyrimidine-6-carboxylic acid hydrochloride (compound 28) and the corresponding free carboxylic acid (compound 2) Following the procedure described in Example 53 using 2-(4-acetyl-1-piperazinyl)-5 ,8-dihydro-8 -npropyl-5-oxopyrido[2,3-d]pyrimidine-6-carboxylic acid, there is obtained 5,8-dihydro-8-n-propyl-2-( lpiperazinyl)-5-oxopyrido[2,3-d]-pyrimidine-6- carboxylic acid hydrochloride m.p. 294 295C with decomposition.

The above hydrochloride (1.0 g) was dissolved in 5 ml of water and neutralized with a 5% aqueous solution of sodium bicarbonate to yield the corresponding free carboxylic acid m.p. 259 -26lC.

Example 56 Ethyl 5,8-dihydro-8-ethyl-2-( l-piperazinyl)-5- 0xopyrido[2,3-d]pyrimidine-6-carboxylate (compound 56) A. A mixture containing 4.5 g of ethyl 5,8-dihydro-8- ethyl-2-(4-trifluoroacetyll -piperazinyl )-5-oxopyrido [2,3-d]pyrimidine-6-carboxylate, 20 ml of a 7% aqueous solution of potassium carbonates, 50 ml of methanol, and 15 ml of chloroform was allowed to react at room temperature for 1.5 hours with stirring. The solvent was then removed by distilltation in vacuo, and the resulting residue was taken up in chloroform. The chloroform solution was dried over anhydrous magnesium sulfate, and the solvent was distilled off to yield a crude product, which was recrystallized from acetone to give 2.9 g of the product m.p. 156 158C.

B. A solution of 3.0 g of ethyl 2-(4-benzyl-1- piperazinyl)-5,8-dihydro-8-ethyl-5-oxopyrid0l2;3d] pyrimidine-6-carboxylate in 100 ml of ethanol was allowed to consume an equivalent amount of hydrogen over 1.5 g of 10% palladium-on-carbon under hydro gen atmosphere. The reaction mixture was filtered to remove the catalyst, and the filtrate was concentrated to give a solid which was collected and'recrystallize'd from acetone. There is obtained 2.5 g of the'product, m.p. 156 -158C.

Example 57 n-Propyl 5 ,8-dihydro-8-ethyl-2-(' 1 -piperazinyl )'-'5- oxopyrido[2,3-d]pyrimidine-6-carboxylate (compound Following the procedure described in Example 56 (B), n-Propyl 2-(4-benzyll-piperazinyl)-5,8-dihydro-8 -ethyl-5-oxopyrido[2,3 d]pyrimidine 6-carboxylate is hydrogenolyzed to yield the product, m.p. 152

I Example 58 (2-ch1oroethy1)-5,8-dihydro-2-( l-piperazinyl)--' oxopyrido[2,3-d]pyrimidine-6-carboxylic acid hydrochloride (compound 63) i A mixture containing 1.0 g of ethyl 2-(4-a c et'ylllpiperazinyl)-8-(2-ehloroethyl)-5,8-dihydro-5 oxopyrido[2,3-d]-pyrimidine 6-carboxylate and 12 ml of aqueous hydrochloric acid was heated on a steam bath for hours, during which period crystals. separated out. The crystals were collected, after. cqoling, and recrystallized from diluted aqueous et hanol containing a small amount of concentrated hydrochloric acid to yield 0.9 g of the product, m.p. 280C with decomposition.

Examples 59 to 61 illustrate the preparation of'the compounds of this invention by the process-(7).

Example 59 i H 5,8-Dihydro-2-(4 methyl-1-piperazinyl) 8 'viny1-5 oxopyrido[2,3-d]pyrimidine-6-carboxylic acid (compound 52) A. To a mixture, containing 60 ml of absolute ethanol due was neutralized with 1 N-hydrochloric acidand extracted with chloroform. The extract was washedwith water and dried over anhydro'us'magnesiurn' sulfate.- 1

The solvent distilled off. The solid that "obtained' was' recrystallized from a mixture of chloroform and etha methyl 1 -piperazinyl )-5-oxopyrido[ 2,3-d lpy'rimidinc- 6carboxylic acid 1.0 g) in 20 ml ofa 10% aqueous solution of sodium hydroxide was heated at 95C for 3 hours. The reaction mixture was then neutralized with hydrochloric acid under ice-cooling and chilled. The resulting precipitate was collected to give 0.63 g of the product. Recrystallization from a mixture of chloroform and ethanol gave the product as pure state.

Example 5,8-Dihydro-2-( l-piperazinyl )-8-vinyl-5- 1 oxopyrido[2,3-dlpyrimidine-6-carboxylic acid hydrochloride (compound 54) To a mixture, containing 400 ml of absolute ethanol and 2.0 g of sodium hydride, which was held at 60C was added with stirring 5.0 g of ethyl 2-(4-acetyll-piperazinyl) -8-(2-chloroethyl)-5,8-dihydro-5- oxopyrido[2,3-d]pyrimidine-6-carboxylate. The resulting mixture was heated to reflux for 2 hours and at the end of the period 200 m1 of water was added. The mixture was refluxed for an additional 30 minutes. The ethanol was distilled off under reduced pressure and the resulting residue was acidified with concentrated hydrochloric acid to pH 1.0. The resulting precipitate was collected and recrystallized from water to yield 2.8 g of the product, m.p. 298 301C with decomposition.

Example 61 5,8-Dihydro-2-( 4-methyll -piperazinyl )-8-viny1-5- oxopyrido[ 2,3-dlpyrimidine-6-carboxylic acid (compound 52) there is obtained the product, m.p. 233 234C.

What is claimed is: 1. Compounds of the formula COOR wherein R, is a moiety selected from one of the group consisting of hydrogen, alkyl having 1 to 4 carbon atoms, hydroxyalkyl having 2 to 4 carbon atoms, bennol to give 0.92 g of the product, m.p. 233 -234C.

(B) A solution of 8-(Z-chloroethyl)-5,8-dihyd 5 carbon atoms substituted by hydroxy or halogen, vinyl,

a'llyl orbenz yl, and R is a moiety selected from one of the'group consisting of hydrogen or alkyl having 1 to 6 carbon atoms; and pharmaceutically effective orgame and inorganic salts thereof. 2. Compounds of the formula 0 COOH wherein R is a moiety selected from one of the group and pharmacuetically effective organic and inorganic consisting of hydrogen, alkyl having 1 to 4 carbon salts thereof.

atoms, hydroxyalkyl having 2 to 4 carbon atoms, phe- 8. A compound of the formula nyl or propargyl, R is a moiety selected from one of the group consisting of alkyl having 1 to 4 carbon 5 O (OOH atoms, alkyl having 2 to 4 carbon atoms substituted by J hydroxy or halogen, vinyl, allyl, or benzyl; i t and pharmaceutically effective organic and inorganic t 1 salts thereof. l 3 i 3. Compounds of the formula 10 CH l 9 coon and pharmacuetically effective organic and inorganic g l salts thereof. 1 i N 15 9. A compound of the formula coon wherein R is the same as defined in claim 2; and pharmacuetically effective organic and inorganic salts i 3 thereof. Hit t N it 4. Compounds of the formula 'H l O m 1 -J( C'H and pharmacuetically efrective organic and inorganic i g salts thereof. 13 1q-'\ 1 \N/ 10. A compound of the ioimi la H==CH 9 OOOH 2 N i Y. wherein R, is the same as defined in claim 2; and phar- 1| maceutically effective organic and inorganic salts (Hwy-p1,)? /"I N thereof.

5. A compound of the formula r,

9 COOH and pharmacuetically effective organic and inorganic salts thereof. l I 11. A compound of the formula \L r-- I I ll N l F? coon 2 v l 1 and pharmacuetically effective organic and inorganic q H I salts thereof.

6. A compound of the formula GH CIECH COCH and pharmacuetically effective organic and inorganic y a salts thereof. I l l 12. A compound of the formula out t. I- l? r1 COOH and pharmacuetically effective organic and inorganic M N salts thereof. A N 9 3H 0 7. A compound of the formula EN N 2 \T. 6 11 i 4 s i 2 l t I I IN T ll N and pharmaeeutically effective organic and inorganic ("LLCU Salts thereof.

J m :i: :3 :g; 

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